PROJECT SUMMARY Power absorption and generation at the ankle is critical to gait efficiency, joint health, residual limb health, and safety in individuals with limb loss. Recent research and commercial efforts have resulted in powered foot-ankle systems, which provide powered-plantarflexion electromechanically, reduce metabolic costs of walking, and show reductions in pathological loading of the contralateral limb. However, these devices are complex, expensive, heavy, and physically large ? all factors which limit widespread adoption. The objective of the energy-havesting mesofluidic impulse prosthesis (e-MIP) is to create an inexpensive, lightweight ankle-foot system that does not require a net energy input for powered push- off plantarflexion and swing phase dorsiflexion. The energy density and bandwidth of high pressure, mesoscale hydraulics enables an ankle that can seamlessly harvest the energy normally dissipated in gait, store energy in fluid accumulators, and reapply the energy in controlled, well-timed power impulses. The benefits of powered systems are therefore realized in an anthropometric size and weight, with a system complexity that is clinically viable.